Maxim Integrated 6612_OMU_S2_URT_V1_13 - Manual (Page 5)

FDD_6612_ 010 6612_OMU_S2_URT_V1_13 Firmware Description Document
Rev. 1.1 5
1 Introduction
This document describes the firmware 6612_OMU_S2_URT_V1_13, which can be used with the Teridian
78M6612 dual outlet power and energy measurement IC. This firmware is designed for single phase
measurement systems using current shunts as the current sensors, but current transformer sensors may
also be used if desired.
Applicability of this firmware is with the Teridian 78M6612 OMU Demo Unit and the Teridian 78M6612
AC-PMON Demo Board. The demo vehicles are calibrated and the user can immediately access
measurement data such as Watts, Voltage, Current, accumulated Energy and line frequency. RTC (real
time clock) is not supported by this firmware.
All measurement calculations are computed by the 78M6612 and this information is communicated to the
host processor. All communication between the 78M6612 and the host processor occurs over a serial
interface (UART0) on the TX and RX pins of the 78M6612 device. The following sections detail the
commands to be sent by the host to configure the 78M6612 and for accessing measurement information.
2 Description of Basic Measurement Equations
The Teridian 78M6612 with firmware 6612_OMU_S2_URT_1_13 provides the user with two types of
continuously updating measurement data (on 1 second increments by default). One is defined as
“Narrowband” (NB) and the other is defined as “Wideband” (WB).
Narrowband measurements are typically used by utilities where the measured waveforms are assumed to
be sinusoidal.
Wideband measurements are generally of interest when measuring nonlinear systems such as switched
mode power supplies that tend to have non-sinusoidal waveforms.
Table 1 lists the basic measurement equations for the Narrowband and the Wideband methods.
Table 1: Measurement Equations Definitions
Symbol Parameter Narrowband Equation Wideband Equation
V RMS Voltage V =
√∑ v
(t)
2
V =
√∑ v
(t)
2
I RMS Current I = S/V I =
√∑ i
(t)
2
P Active Power P =
∑ (i
(t) *
v
(t)) P =
∑ (i
(t) *
v
(t))
Q
Reactive
Power
Q =
∑ (i
(t) *
v
(t)shift 90º) Q =
√(S 2
– P
2
)
S
Apparent
Power
S =
√(P 2
+ Q
2
) S = V * I
PF Power Factor P/S P/S
PA Phase Angle ATAN (Q/P) ATAN (Q/P)
Both types of measurement outputs are continuously available to the user. To obtain measurement
outputs, the serial UART interface between the 78M6612 and the host processor must be set up and is
described in the next section.